Channelrhodopsins (ChR) are one of a selection of light sensitive proteins found on the surface of algae that act to move the algae towards or away from light to find the ideal illumination for photosynthesis. The ChR acts as an ion channel in the cell surface opening in response to stimulus by set wavelengths causing activation of flagella. By genetically targeting cells in specific brain neuron populations to express one of these proteins, ion channels can be opened causing neuron excitation when illuminated with light.
Alternatively, other surface proteins can be expressed that inhibit the action of the neuron. Using this combination of neuron targeting, protein selection, genetic modification, and selective highly focused light, great benefits over previous neuron manipulation techniques, which relied on electrical stimulation, can be achieved.
This technique of optogenetics is a growing area of scientific research that controls and studies the behaviour of neurons by the illumination with light.
By studying the role of neurons in precise areas of the brain, more can be learnt about the functions of the brain and by extension its malfunctions. This understanding leads to increased possibilities for therapies for many brain disorders including Parkinson’s disease, Tourette’s syndrome, schizophrenia and OCD.
To provide illumination, the use of lasers has a number of benefits:
- They have relatively high power that allow beam splitting to form arrays, offering control over the location of illumination in the living brain.
- They are wavelength specific and so can be paired with individual proteins.
- The beams can be easily controlled through fibres to deliver the excitation the desired area.
- They can they be modulated.
Choosing the right laser wavelength, power and delivery method is defined by the application in mind. Laser Quantum offers a wide wavelength range (473 to 1064nm) that covers many of the required protein actuators.
gem family of lasers: Small, stable and powerful and can be fibre coupled for easy beam manipulation
ventus family of lasers: Improved power stability, higher controllability, and fibre coupled availability
473nm many ChR variants
532nm for ChR, C1V1 etc
561nm for Arch and eBR
660nm for eNpHR-3